Selector switch for automatic telephones



Sept. 13,1949. c. E. LOMAX SELECTOR SWITCH FOR AUTOMATIC TELEPHONES Filed Sept. 5, 1946 [NV EN T 0R. CLARENCE E. LOMAX ATTORNEY Patented Sept. 13, 1949 llNlTED STATES P TENT OFFICE SELECTOR swrrcn FOR AUTOMATIC TELEPHONES Clarence E. Lomax, Chicago, IlL, assignor to Automatic Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application September 5, 1946, Serial No. 695,011

8 Claims.

This invention relates in general to selector switches in automatic telephone systems, and more particularly to a novel circuit arrangement for a battery searching selector switch of the ten level twenty trunk type.

The object of this invention is to provide a novel controlling circuit which enables automatic selecting operations at maximum speed and with a high degree of accuracy and a circuit arrangement which lends itself to ready conversion for use in systems having different numbers of trunks.

'A feature of the invention is the manner in which the cam relay and the ofi normal relay are arranged to alleviate the usual spring load on the release relay.

A further feature is the manner in which the cam relay and the off normal relay are arranged to effect application of dial tone to the line in seizure of the selector and to remove same so that it will not be heard at the end of the first digit.

Another feature is the manner in which both testing relays are arranged so as to operate simultaneously if they find an idle contact at the same time, the operation of one of the testing relays and the associated switching relay preventing operation of the switching relay associated with the other testing relay.

Other objects and features of this invention will become apparent upon reference to the specification and accompanying drawing,

Referring now to the drawing, the automatic telephone system thus illustrated incorporates the features'of the applicants selector circuit and includes a substation I, finder switch 2, the battery searching selector circuit '3, connector 4, and a second substation 5.

The selector is connected to the finder 2 by conductors I33 to I31 inclusive and is controlled to operate by impulses transmitted from substation I in a well known manner to position the wipers I38 to I43 inclusive opposite a desired group of bank contacts which are connected by trunk lines to connectors such as 4, which further extends the call to subscriber 5. Essentially the battery searching selector circuit consists of a well known Strowger vertical and rotary switch having off normal springs I49, and cam springs I46 used in conjunction with a circuit including testing relays I0 and 20, switch through relays 30 and 40, line relay 50, release relay 60, cam release relay 10, vertical 'ofi normal relay 80, change over relay 90, vertical magnet I00, release magnet III! and rctary magnet I20, their associated contacts and connections. The finder switch is of the type disclosed in application Ser. No. 702,846, filed October 11, 1946.

It will now be assumed that the calling subscriberat substation I wishes to extend a connection 'tosub'scriber 5. On removal of the receiver, 'a connection is initiated through the finder 2 in 2 v a well known manner over connectors I 33, I34, I35, I36 and I31. When this selector switch is thus seized, a loop circuit is closed for line relay 59 and a ground is connected by the finder'to conductor I31, over contact 83 to relay 9!]. Relay 99 operates and at its contacts 92 opens a point in the operating circuit of magnet I20, and at its contacts 9| prepares a point in the operating circuit of vertical magnet I00 and prepares a self holding circuit. Relay 50 operates and at its contacts 5I closes an operating circuit to relay 60 over contacts 31, 41 and El, and at its contacts 52 opens another point in the release magnet operating circuit. Relay 69 operates and at its contacts 6| places ground on conductor I31 to hold; the finder 2, at its contacts 62 prepares a point in the holding circuit to relay 90 and the vertical magnet I00, at its contacts 63 opens a further point in the operating circuit of the release magnet I Ill, and at its contacts 64 completes an operating circuit to relay 1!] over normally closed cam spring contacts I46. Relay 10 operates and at its contacts TI opens a point in the busy tone circuit, at its contacts 12 completes a dial tone circuit over contacts 85, 12, 4I, 3I' and conductor I35, at its contacts 14 prepares an operating circuit for relay 2, at its contacts 15 prepares an operating circuit for relay II], at its contacts 16 completes a circuit for permanent signal supervision over contacts 16, 22, I2, 39, 49, HI, 81 and conductor I48, and at its contacts 11 starts the dial tone generator. The selector is now prepared for receipt of impulses from substation I, relays 50, 99, 10 and 90 being in the energized condition. On receipt of the first break of the first impulse, line relay 5!] deenergizes and at its contacts 5! opens the operating circuit to relay 60 and at its contacts 52 closes a point in the holding circuit to relay 99 and completes the circuit to vertical magnet I00 over contacts 31, 41, 52, 62 and 9|. Vertical magnet Illll operates and elevates the wipers I38 through I43 inclusive one step whereby they are positioned in a well known manner opposite the first level of bank contacts in the associated contact field. Incident to the first vertical step, the vertical off normal springs I49 are closed and complete a, circuit to relay 80. Relay operates and'at its contacts 8I removes ground from the lead I33 to the finder 2, at its contacts 82 places ground on the guard lead I34 to the finder, at its contacts 83 opens the operating circuit to relay 90, atits contacts 83' completes the afore mentioned holding circuit to relay 90, at its contacts 84 prepares the busy circuit to the line, at its contacts 85 disconnects the dial tone cord from the line, at its contacts 85 prepares a point in the circuit to the release magnet III), at its contacts 86 prepares a circuit to the rotary magnet I20 and at its contacts 81 opens the circuit to the permanent supervisory shelf lamp over lead I48. The

' 3 advantage in opening the all trunks busy lead I33 at contacts BI lies in the fact that the ground will be kept 'from theall trunks busy lead if the finder releases and the selector does not. The vertical magnet elevates the wipers a number of levels relative to the number of impulses received. Relay 60 is slow to release and'holds up during the pulsing, being aided in its energization during each make period of the incoming pulses; Relay 9B is also slow to release and is aided to hold dur ing the series of incoming pulses on each break period of the impulses. I

A short period after the cessation of impulses of the first digit, relay 90 releases, and at its contacts 9| opens its self holding circuit, and at its contacts 92 completes the self interrupting operating circuit to-rotarymagnet I20, over cone tacts 1-6, 22, I2, 39, 149 121,88 and .92. If all trunk lines on the selected level are busy the switch wipers will he stepped in a well known manner -:tothe eleventh position, whereupon .the cam springs I4'6-aare operated to close the opera. ating circuit to the busy tone generator .and to open-the operating circuit for relay 10. Relay 10 at its contacts 'I:I applies busy .tone to the finder over line 135 and contacts .34, EN, 14!, and 32I, at its contacts 12 further opens the dial .tone on: cuit to line I35, at its' cOntacts-T'M opens the lprfia pared circuit to relay 20, .at its contacts 15 opens the prepared circuit to relay 1:0, and at itscone tacts I6 :opens :the circuitiito the rotary magnet. l he calling party on receipt of the busy. time restores wh'ichopens thecperating circuit to relay -50. Relay 50 releases and-at alts contacts 54 opens the circuit torelayfill. Relay an releases and at its .con'tacts :BI. removesground irom c'on'ductorI3'I to the finder, at its contacts .62 further opens the circuit .110 relay 99 .and magnet ='I:-00, a't its contacts 63 completes acircuit to ithe release magnet -I:I=I) over-contacts 371, .41, :52, 63 and 85, :and at its contacts :64 further opens the circuit to relay Ill. Magnet eI IEI operates .and releases the switch thereby opening the .operat: ing circuit to relay .80. Relay so restores and theswitch is then ready for a subsequent :call.

If the selected level is not busy, :the switch will stop :rotating when either .of the wipers Ail-2 :or .I43 cri-both findan idle trunk .withbatterypotential thereon, Assuming wiper I43 .finds bat .tery, a circuit will be .completed :for relay over contacts 38 and :14. Relay .20 operates and at its contacts 2I completes an loperatingcireuit to relay! .over contacts .ZI .and.16,.and;at its contacts 22 opens the operating circuit to the rotary magnet I20. The rotary motion of the switch' is stopped therapy. Relay .40 operates and at its contacts '4 I and 43 opens i-theoperating circuit .to line :relay 50; at alts :contacts :42 and connects lines 135 and 1.36 :from "the finder to line I38and I40 whicharleconnected to :the. idle trucks of :the first group of trunks of" the selector, at .its contacts :45 .connects line I31 to .line I43 and thereby extends the Gleadithroush the selector, at itscontacts dB closes a tempo? .rarylholding circuit for .itself over zeontacts 1B] and 46,:at its contacts 1 41 .opens: a further point in :the operating". circuit of :the release .magnet M0, at. its contacts 48 .opens apoint in :t-l'ie ope. crating circuit of relayrID, and at its contacts :49 opens a lf111thl21:.p0lnt-in ztheoperatinghirouit or rotary magnet 12!). .If :thetfirstztested trunk :of thefirst group ofxtrunks wereiiound busy; and the tested trunk of .theseccnd e oupof tru ks wer not busy wiper I42 wouldrhave been 10ccnected to battery potential on thelfirst-idlertrunlt of the second group and relays I0 and 30 would haveoperated in the same-manner as-relays 20 and 40 were operated." It is evident that leads I35 and I36 would then be connected to leads I31 and MI. If both wipers I42 and I43 find battery they will try to operate simultaneously.

Either relay It or'relay 20 will operate first. As-

I fi -y, .groundis connected over these wipers through the resistance of relays: III andzll respectively. Assuming relay; it operated first. An operating circuit to relay .40 is completed as previously. described. Relay. 4!] energizestand at its contacts 48' removes theerouncl to relaylll and wiper I42. In. this fashion theeround throu h relay "Ill is removed fromthe test wiper and eliminates the possibility of the QOH-sSfiiZBd; trunk testin busy :to other switches. a

Relay 15B restores as described. above and at its contac s .51 opens the operatingcircuit to relay .60. and at its contacts 152 closes a point in the operat n .circuitsfor. release ma net 11.0. Relay cc releases after an intervalsand at. its

con acts BI removes ground from conductor 51.31 I

to the finder, at its contacts 152 further. opens the operatin circuit .to vertical magnet Inn, at

itscontacts .63 further prepares the .opera-tingnirs cult 'to' release magnet Illl andat its contacts .inithe .busy tone .oirou-it, at its contactsfllium ther opens the dial tone circuit to the line .at

ts contacts 1.4. opens the operating circuit to relay 120, at its-con acts FIE-opens the operating circuit to relay It, and at its contacts flfi opens the opera ing circuitto relays stand 40; Assumin that rel y .4!) -.is.-the operated relay, lit ill be held u by a ground returned ioveriwiper-JM .and contactsi as. iand'v4fi 'from thesumeeding switch. :The call is new extended ithrough-sthe oniector and re ays.40-;and 18fl'are held .ener, g ze,

Release of the switch isefiectedin a normal manner. When the called partyhangsup ground is removed i-from wiper I-.4.3.:by the connector 4 andrelay .40 releas s and at? its contactszfl and 4.3 prepares. the line circuit -of the selector-tier subsequen calls r m val of ground from wiper 1.43am onduct r it? also eausesirelease of the find r 2- R lay 4.0 at ts contacts 146 further Qp ns -:its s l hold n circ it, at its contents 4:7 comple s a opera-tine ir uittorclease relay I I 0 ove con a ts3 .4 .152.363-and55. .helease re ay I perates and efieet release oi the se le tors it h in aiwe l nown manner. Theofi norma spr n s 4. op n c rcui to .--reley.9 wh ch; elea es and .et-its contacts 5 .r epnli s ar und to the ATB ead 1.33, I.

c n ac sflz removes groundlfmmthe guard? ad to finde :2, atits c ntest 815 trees the o erate ins eir u to th e eas moo stone at its o e teats-3, 84, Mend i i-prepar s t s l .ouit for: ub equen on rai on. She-rel as e a net releases and the selector isrestcred tp n ltis anew.toe-entreeseasement ylqersasilv his .19 levelaeao ..trunk,selectq connected team-19 or .az;l-l efi0:-;sslestcr v oer 2. a ts adding or removing sets of relays similar to relays l and 30 with the associated wipers and banks therefore.

While a particular embodiment of the invention has been described, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention.

What is claimed is:

1. In a telephone system, a trunk line terminating in a two-motion automatic switch, means for seizing said switch over said line and operating same, a source of dial tone, a set of ofi normal springs and a set of cam springs in said switch, a a cam relay in said switch having its operating circuit controlled by said cam springs, an off normal relay having its operating circuit controlled by said oiT normal springs, said cam relay operated responsive to seizure of said switch over said line to connect said source to said line, said off normal springs operated responsive to an initial movement of said switch to operate said ofi normal relay, means responsive to an operation of said 01f normal relay to remove dial tone from said line prior to termination of the initial movement of the switch, a source of busy tone, and means for at times operating said cam springs to terminate the secondary movement of said switch and to connect said latter source to said line.

2. In a two-motion automatic switch having a set of off normal springs, a set of cam springs and incoming connections, a cam relay having its operating circuit controlled by said cam springs, an ofi normal relay having its operating circuit controlled by said off normal springs, said cam relay operated Whenever said switch is seized over said incoming connections, two switch operating magnets having operating circuits arranged to operate said switch in its primary movement and its secondary movement respectively, said off normal relay operated when the switch is operated in its primary movement by one of said magnets, said cam relay and said off normal relay arranged in combination to control the operating circuit of the other of said magnets to move the switch in its secondary movement.

3. In an automatic switch as claimed in claim 2 in which said cam springs are operated at times during said secondary movement to open the operating circuit of said cam relay, means operated responsive to release of said cam relay to prevent further operation of said other magnet, means operated to release said switch, said cam springs being effective to prevent operation of said other magnet on operation of said release means.

4. In an automatic switch having contacts connected at times to negative battery potential, incoming connections, a set of cam springs, a cam relay operated responsive to seizure of the switch over said incoming connections, an operating circuit for said cam relay controlled by said cam springs, a plurality of testing relays, a plurality of switching relays, each of said plurality of testing relays associated with each of said plurality of switching relays, operating circuits for said testing relays and said switching relays prepared responsive to operation of said cam relay, means for moving a plurality of the test wipers of said switches over said contacts in search of an idle contact, each of said plurality of testing relays connected to each of said plurality of wipers, one

of said testing relays and its associated switching relays operated when its associated wiper engages a contact having a negative battery potential thereon, said one testing relay and its associated switching relay operated to prevent any other of said plurality of switching relays from operating while the said one testing relay is operated.

5. In an automatic switch having contacts connected at times to negative battery potential, a plurality of testing relays, a plurality of switching relays, incoming connections, operating circuits for said testing relays and said switching relays prepared responsive to seizure of the switch over said incoming connections, means for moving a plurality of the wipers of said switch over said contacts in search of an idle contact, each of said plurality of testing relays associated with one of said plurality of switching relays and one of said plurality of wipers, a plurality of said testing relays operated when the wipers associated with said plurality of testing relays simultaneously engage a contact having negative battery potential thereon, one of said testing relays and. its associated switching relay operative to prevent the switching relays associated with the other of said plurality of operated testing relays from operating.

6. In a telephone system, a trunk line terminating in an automatic switch, means for seizing said switch over said line and operating same, a relay having a single winding, a relay circuit including said single winding energized to operate said relay responsive to seizure of the switch, a pulsing circuit in said switch for operating said switch in a stepping operation in response to incoming impulses, a second relay, circuit means for operating said second relay responsive to said stepping operation of said switch, contacts operated by said second relay for disconnecting said relay circuit from said seizing circuit and for connecting said relay circuit to said pulsing circuit to thereafter control the operation of said single winding relay over said pulsing and relay circuits during said stepping operation.

7. In an automatic switch as claimed in claim 6 in which said switch has means for causing a secondary movement of the switch, said secondary movement means including contacts closed responsive to said release of said single winding relay for operating said secondary movement means.

8. In a two motion switch as claimed in claim 2 in which said cam relay is in the operated condition to effect said operating circuit of the other of said magnets to cause said switch to move in its secondary movement, and means for operating said cam springs responsive to said switch reaching a predetermined point in its secondary movement to effect release of said cam relay, said cam relay thereby operated to control said operating circuit to prevent said other magnet from moving said switch further in its secondary movement.

CLARENCE E. LOMAX.

REFERENCES CITED The following references are of record in the file of this patent:

V UNITED STATES PATENTS Number 

